1. Field of the Invention
The present invention relates to an artificial lens for eyes and a method of locating the lens on the cornea, and particularly to a lens and method for fixation of the lens to the eyeball.
2. Description of the Prior Art
Contact lens adapted to fit over the cornea of the eye are well known in the prior art. They are made from so-called "hard" materials which are generally inflexible and typically 81/2 to 9 millimeters in diameter. The relatively large diameter of the lens results in eye irritation after prolonged periods of wearing. The cornea requires continuous oxygen replenishment and continuous removal of carbon dioxide concentrations. The tear film washing over the corneal surface normally accomplishes this. However, the relatively large contact lens covering the cornea interferes with this function of the tear film. Various attempts have been made to reduce the amount of the lens in actual contact with the cornea, such as by cutting openings or fenestrating the lens, or by undercutting the margins of the lens. This has been successful only to a limited extent.
So-called "soft" are made of a material generally conformable to the curvature of the individual cornea. They are therefore characterized by less irritation. In addition, the lens material is relatively porous and provides a degree of lubrication and tearing not possible with a hard lens. The gas permeable character of the lens material also promotes oxygenation of the corneal surface and removal of carbon dioxide concentrations. However, such soft lenses tend to harbor and promote growth of undesirable bacteria, and scrupulous care must be exercised to maintain the soft lens in a sterile condition to avoid eye irritation.
The foregoing lens types are typical of prior art attempts to provide a lens large enough to utilize the spherical surface of the cornea for self-centering adjacent the pupillary zone of the cornea, and with provision for tear film access to the corneal surface underlying the lens. Enlargement of the lens surface to enhance self-centering of the lens usually results in eye irritation, while any significant reduction of the lens surface area achieves improved tearing of the corneal surface at the expense of proper optical positioning of the lens.
Neither soft nor hard lenses are normally designed to maintain a fixed rotative position relative to the eye. Consequently, it is difficult to grind the lens to correct for astigmatism along a diametral axis of the lens. Various means have been attempted which tend to prevent a lens from rotating, such as by having the lower margin of the lens ground to provide a chord adapted to ride against the lower eyelid, or by weighting of the lens so that a particular portion is always oriented downwardly, but such lenses have met with only limited success.